7065-132I • May 18, 2017
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www.heatilatorecochoice.com
Negative pressure results from the imbalance of air avail-
able for the appliance to operate properly. It can be stron-
gest in lower levels of the house.
Causes include:
• Exhaust fans (kitchen, bath, etc.)
• Range hoods
• Combustion air requirements for furnaces, water
appliances and other combustion appliances
• Clothes dryers
• Location of return-air vents to furnace or air conditioning
• Imbalances of the HVAC air handling system
• Upper level air leaks such as:
- Recessed lighting
- Attic hatch
- Duct leaks
To minimize the effects of negative air pressure:
• Install the outside air kit with the intake facing prevailing
winds during the heating season
• Ensure adequate outdoor air for all combustion appliances
and exhaust equipment
• Ensure furnace and air conditioning return vents are not
located in the immediate vicinity of the appliance
• Avoid installing the appliance near doors, walkways or
small isolated spaces
• Recessed lighting should be a “sealed can” design
• Attic hatches weather stripped or sealed
• Attic mounted duct work and air handler joints and seams
taped or sealed
• Basement installations should be avoided
WARNING
• Negative pressure can cause spillage of com-
bustion fumes, soot and carbon monoxide.
• Appliance needs to draft properly for safety.
Asphyxiation Risk.
C. Negative Pressure